Oscillator-translator system



Dec.-l6, 1941. I w. s. WINFIELD 2,266,670 I OSCILLATOR-TRANSLATOR SYSTEM Filed Jan. 28, 1941 INVENTOR M41. MM 5. MAI/754.0

ATTOR N EYY Patented Dec. 16, 1941 OSCILLATOR-TRANSLATOR SYSTEM William S. Winfield, Buffalo, N. Y., assignor to Colonial Radio Corporation, Buffalo, N. Y.

Application January 28, 1941, Serial No. 376,299

13 Claims.

This invention relates to improvements in oscillator-translator systems, wherein oscillae tions of a desired frequency-which may include' one or more bands of frequencies-are generated and supplied to a translator wherein they are combined with oscillations of another frequency which may be one of a band or bands of frequencies.

My invention is of particular utility in radio receivers of the superheterodyne type but as will be understood, is not limited in its application thereto, but may be advantageously employed wherever oscillator translator systems are used.

In such systems as heretofore constructed it has been impossible to achieve the theoretical sensitivity and signal to noise ratio over a frequency band because of deviations from the optimum operating conditions of the system.

Among the reasons which may be mentioned causing these deviations are variations in the oscillator voltage from one end of the tuning range to the other, and in quantity production receivers, deviations due to oscillator tube and circuit production variations.

Among the objects of my invention may be mentioned:

To obtain maximum conversion output of the translator at all times and under all conditions, thus providing maximum signal to noise ratio.

To increase the gain, permitting either higher overall gain in the receiver or decreased cost with the same gain.

To greatly simplify the problem of obtaining proper oscillator excitation particularly at extreme ends of the tuning band and with fluctuations of power line voltage.

To reduce the Variations in sensitivity which occur between various translator tubes when they are employed in the same circuit.

To simplify the oscillator coil design, reducing the time required to assemble the set and reducing the number of parts required; particularly the parts heretofore believed necessary to give a flat characteristic for oscillator injection voltage.

Still other objects of my invention will be apparent from the specification.

In this application I have particularly pointed out and distinctly claimed, the part, improvement or combination which I claim as my invention or discovery and I have explained the principles thereof and the best mode in which I have contemplated applying those principles so as to distinguish my invention from other inventions.

In the drawing, the figure is a circuit diagram showing my invention.

In accordance with my invention, I derive from the oscillator the desired magnitude of voltage to be injected into the translator. Any translator' tube has an optimum ratio of oscillator injection voltage to D. C. bias voltage. In systems of the type to which my invention applies, departure from this optimum ratio under various conditions has been responsible for various difficulties some of which were mentioned above.

I avoid or reduce these difiiculties and improve the performance of the system in the above mentioned respects by maintaining at all times the optimum ratio between the oscillator injection voltage and the translator grid bias. This may be done by taking the oscillator injection voltage, rectifying it, controlling the circuit in such a manner that the rectified voltage has the desired optimum ratio to the injection voltage at all times, and applying the rectified Voltage so derived and controlled, to the translator grid as a bias.

Referring now more particularly to the circuit diagram, l represents an antenna of any suitable type, connected through inductance 2 to ground. Coupled to inductance 2, there may be provided another inductance 3, forming with tuning condenser 4 the tuning circuit in the input of translator tube 5. It will be understood that other suitable input circuits may be employed, such for example as a loop antenna connected in place of inductance 3.

The translator tube may be an indirectly heated triode having a cathode 5a., heater 5b, control electrode or grid 50, and anode 5d, but it will be understood that other types of tubes may be employed, if desired. The output circuit of the tube 5 may comprise inductance I3 tuned to intermediate frequency by condenser l4, connected to ground through condenser 15, and to the source of plate voltage, not shown. Cou pled to inductance I3 there may be provided inductance 16, also tuned to intermediate frequency by condenser II.

From this point on, through the intermediate frequency amplifier, second detector, and audio frequency amplifier, any suitable and well-known super-heterodyne construction may be employed, and since the same is, per se, no part of my invention, it is not shown or described in detail.

From the low potential side of inductance 3, there may be a connection to ground through condenser E, and a connection through isolation resistance 1 to the plate of diode l2. Diode l2 may be a separate tube having a cathode 12a, heater 12b, and anode lZc, or the anode and cathode may be incorporated within the envelope of another tube in the Well-known manner. Connected between the cathode and anode of diode i2, there may be provided resistance In, the cathode side of which may be connected to ground. The anode of diode I2 may be connected through condenser H to conductor 8 which may beconnected between the cathode 5a of translator tube 5 and the circuit of oscillator tube 24.

Oscillator tube 24 may be a triode having cathode 24a, heater 241), control electrode 240, and anode 2m. Any suitable oscillator circuit may be employed, such as inductance 23 connected at one end to grid 24c, and at the other through resistance 25 shunted by condenser 26 to ground. The anode 24d may be connected to a source of power, and to ground through condenser 28. Tuning condenser 2| may be connected from the top end of inductance 20 to ground, and grid condenser 22 may be provided, as well as leak resistance 23 from grid 240 to cathode 2 5a. Conductor B may be connected to a suitable point on inductance 2i] chosen to deliver the desired injection voltage to the translator.

In operation, the desired portion of the oscillator voltage is impressed between the cathode 5a and grid 50 of the translator tube 5, to heterodyne the incoming signals, in the well-known manner. Also, this portion of the oscillator voltage is impressed through condenser II on the diode I 2, and there rectified. This produces a direct current voltage making the diode anode 12c negative with respect to cathode 12a, and this negative voltage is impressed between the cathode 5a and grid 50 of translator tube 5, making the latter more negative than the former. It will be seen that this bias is proportional to the magnitude of the oscillator voltage impressed on the translator, because of the linear rectification characteristic of the diode over the range of voltages employed.

The actual ratio between the injected oscillator voltage and the bias applied to the translator may be controlled by choice of the Value of resistance 25, which may be made variable, if desired, but which may and preferably will be initially selected to give the desired voltage ratio for the tube employed as the translator.

It will be noted that since the portion of inductance 20 between conductor 8 and ground is included in the plate load circuit of the translator, on high signal inputs, a portion of the output of the translator (mostly si nal frequency) is also rectified by diode I2 and impressed as an additional bias upon the grid of the translator. This serves to prevent overloading of the translator on strong signals.

If a separate coil coupling is used between the oscillator and the translator, instead of the autotransformer coupling shown, the impedance may be adjusted to give the desired high signal control and the coupling adjusted to give the desired injection voltage.

While I have shown and described certain preferred embodiments of my invention, it will be understood that modifications and changes may be made without departing from the spirit and scope of my invention, as will be understood by those skilled in the art.

I claim:

1. In combination, a translator having a cathode, an anode, and a control electrode, an oscillator, means for providing cathode injection of oscillator voltage into said translator, and means for applying a grid bias to said translator linearly proportional to the magnitude of the oscillator voltage injected therein.

2. In combination, a translator having a cathode, an anode, and a control electrode, an oscillator, means for supplying oscillator voltage to said translator, and means for applying to said translator a grid bias voltage linearly proportional to the magnitude of the oscillator voltage supplied thereto.

3. In combination, a translator having a cathode, an anode, and a control electrode, an oscillator, means for supplying oscillator voltage to said translator, and means connected in the plate circuit of said translator for applying to said translator a grid bias voltage having a component linearly proportional to the output of said translator.

4. In combination, a translator having a cathode, an anode, and a control electrode, an oscillator, means for supplying oscillator voltage to said translator, and means connected in the plate circuit of said translator for applying to said translator a grid bias voltage having a component linearly proportional to the output of said translator, and a component proportional to the magnitude of the oscillator voltage supplied to said translator.

5. In combination, a translator having a cathode, an anode, and a control electrode, an oscillator, means for supplying oscillator voltage to said translator, a rectifier, means for supplying to said rectifier the same voltage supplied to said translator from said oscillator, and means for impressing the output voltage of said rectifier as a bias upon the grid of said translator.

6. In combination, a translator having a cathode, an anode, and a control electrode, an oscillator, means for supplying oscillator voltage to said translator, a rectifier having a cathode and an anode, means for supplying to said rectifier the same voltage supplied to said translator from said oscillator, and a direct current connection from the anode of said rectifier to the control electrode of said translator.

'7. In combination, a translator having a cathode, an anode, and a control electrode, an oscillator, a portion of the output circuit of said translator being included in the circuit of said oscillator, means for supplying oscillator voltage to said translator, a rectifier, means for supplying to said rectifier the same voltage supplied to said translator, and means for impressing the rectified voltage from said rectifier as a grid bias upon said translator.

8. In combination, a translator having a cathode, an anode, and a control electrode, an oscillator, a portion of the plate circuit of said translator being included in the circuit of said oscillator, means for supplying to the input circuit of said translator the voltage developed across said portion of the translator plate circuit, means for rectifying said voltage, and means for impressing said rectified voltage as a grid bias upon said translator.

9. In combination, a translator having a cathode, an anode, and a control electrode, an oscil- 1ator, a portion of the output circuit of said translator being included in the circuit of said oscillator, means for supplying by cathode injection to said translator the voltage developed across said portion of the translator output circuit, means for rectifying the same voltage, and means for impressing said rectified voltage as a grid bias upon said translator.

10. In combination, a translator having a cathode, an anode, and a control electrode, an oscillator having an anode, a cathode, and a control electrode, an inductance connected between the control electrode and anode of said oscillator, a connection between the cathode of said translator and an intermediate point on said inductance, a rectifier having an anode and a cathode and having its anode connected through an impedance to said connection, and a direct current connection from said rectifier anode to the control electrode of said translator, said last connection including a resistance.

11. The method of operating an oscillatortranslator system employing a translator having a cathode, an anode, and a control electrode, which comprises supplying signals to said translator, generating oscillations to be combined with said signals, supplying said oscillations to said translator, deriving from said oscillations a unidirectional potential difference proportional to the magnitude of said oscillations, and impressing said potential difference between the cathode and control electrode of said translator as a bias.

12. The method of operating an oscillatortranslator system employing a translator having a cathode, an anode, and a control electrode, which comprises supplying signals to said translator, generating oscillations to be combined with said signals, supplying said oscillations to said translator, rectifying said oscillations to produce a unidirectional potential difference proportional to the magnitude of said oscillations and having a desired ratio thereto, and impressing said, potential difference between said cathode and control electrode as a bias.

13. The method of operating an oscillatortranslator system employing a translator having an anode, a cathode, and a control electrode, which comp-rises sup-plying signals to said translator, generating oscillations to be combined With said signals, supplying said oscillations to said translator, deriving from the output of said translator and from said oscillations a unidirectional potential difference having a component proportional to the magnitude of said oscillations, and impressing said potential difference between the cathode and control electrode of said translator as a bias.

WILLIAM S. WINFIELD. 

